View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by ethesis@nitr Design of a Boost Converter Submitted by Abdul Fathah (109EE0612) Department of Electrical Engineering National Institute of Technology Rourkela - 1 - Design of a Boost Converter A Thesis submitted in partial accomplishment for the degree of Bachelor of Technology in “Electrical Engineering” By Abdul Fathah (109EE0612) Under guidance of Prof. B.D. Subudhi Department of Electrical Engineering National Institute of Technology Rourkela-769008 (ODISHA) June-2013 - 2 - DEPARTMENT OF ELECTRICAL ENGINEERING NATIONAL INSTITUTE OF TECHNOLOGY, ROURKELA ODISHA, INDIA-769008 CERTIFICATE This is to certify that the thesis entitled “Design of a Boost Converter”, submitted by Abdul Fathah (Roll. No. 109EE0612), in partial fulfillment for the award of Bachelor of Technology in “Electrical Engineering” during session 2012-2013 at National Institute of Technology, Rourkela. An authentic record of research work carried out by him under my supervision and guidance. The student has fulfilled all the recommended requirements. The Thesis is based on candidate’s own work, has not submitted elsewhere for a degree/diploma. In my opinion, this thesis is of standard required for the award of a bachelor of technology degree in Electrical Engineering. Place: Rourkela Dept. of Electrical Engineering Prof. B.D. Subudhi National institute of Technology Project Supervisor Rourkela-769008 - 3 - ACKNOWLEDGEMENTS On the submission of my thesis entitled “Design of a Boost Converter”, as a final year project, I would like to extend my appreciation & my sincere thanks to my project supervisor, a very generous guide in fact, Prof. B.D. Subudhi, Department of Electrical Engineering for his ceaseless encouragement and support during the course of my work. I verily appreciate and value his prestigious guidance and motivation from the beginning to the end of this work. His knowledge and support at the time of crisis will be remembered lifelong. He has been great source of inspiration to me and I thank him from the bottom of our hearts. I would also like to thank the staff of Electrical engineering department for constant support and providing place to work during project period. Last but not the least I would also like thank my friends, specially Soumya Ranjan Panda and Subhransu Satpathy who was with me during thick and thin. Abdul Fathah B. Tech (Electrical Engineering) a Dedicated to My beloved parents b ABSTRACT The switching mode power supply market is flourishing quickly in today’s world. Design engineers aren’t always supplied with the desired amount of voltage they need in order to make their design function properly. Adding an extra voltage supply to a design is not always cost efficient. This thesis is proposed to provide the designer with a method of boosting DC voltage from 5 Volts to 15 Volts, by using a boost converter designed specifically for this task. All aim, calculations, tests, data and conclusions have been documented within this report. Results of simulation show that the switching converter will boost voltage from 5 volts to 15 volts with power conversion efficiency of 94.16 percent. i CONTENTS ACKNOWLEDGEMENTS a ABSTRACT i TABLE OF CONTENTS ii LIST OF FIGURES iv CHAPTER 1 INTRODUCTION 1 1.1 RATIONALE 1 1.2 PURPOSE OF THE PROJECT 1 CHAPTER 2 BACKGOUND AND LITERATURE REVIEW 2 2.1 OVERVIEW 2 2.2 HISTORY 2 2.3 APPLICATIONS 2 CHAPTER 3 METHODOLOGY 4 3.1 GENERAL BOOST CONVERTER CONFIGURATION 4 3.2 BLOCK DIAGRAM 8 3.3 SPECIFICATIONS 9 3.4 COMPONENT FUNCTIONS 9 3.5 COMPONENT CALCULATIONS 9 3.5.1 LOAD RESISTANCE 9 3.5.2 DUTY CYCLE 9 3.5.3 CAPACITOR 10 3.5.4 INDUCTOR 10 3.5.5 DIODE 11 3.5.6 MOSFET 11 ii 3.6 LOSS CALCULATION 11 3.6.1 DIODE LOSS 11 3.6.2 SWITCHING LOSS 12 3.6.3 GATE CIRCUIT LOSS 12 3.6.4 CONDUCTION LOSS 12 3.7 EFFICIENCY 13 3.8 TRANSFER FUNCTION 13 CHAPTER 4 RESULTS AND OBSERATIONS 18 4.1 MATLAB SIMULATION RESULTS 18 4.2 PSPICE SIMULATION RESULTS 19 4.3 OBSERVATIONS 20 CHAPTER 5 CONCLUSION 21 REFERENCES 22 iii LIST OF FIGURES Figure 3.1.1 - Circuit Diagram of Boost Converter 4 Figure 3.1.2 - Circuit operation (a) Mode 1 and (b) Mode 2 5 Figure 3.1.3 – Waveforms 6 Figure 3.2.1 - Block diagram 8 Figure 3.8.1 - Switch ON equivalent Circuit 13 Figure 3.8.2 - Switch OFF equivalent circuit 16 Figure 4.1.1 - Circuit Diagram of Boost Converter used in MATLAB 18 Figure 4.1.2 - IO (output current) vs Time in MATLAB 18 Figure 4.1.3 - VOUT(output voltage) vs Time in MATLAB 19 Figure 4.2.1 - Circuit Diagram of Boost Converter used in PSPICE 19 Figure 4.2.2 - VOUT(output voltage) vs Time in PSPICE 20 iv Chapter 1 INTRODUCTION 1.1 RATIONALE In many technical applications, it is required to convert a set voltage DC source into a variable-voltage DC output. A DC-DC switching converter converts voltage directly from DC to DC and is simply known as a DC Converter. A DC converter is equivalent to an AC transformer with a continuously variable turns ratio. It can be used to step down or step up a DC voltage source, as a transformer. DC converters are widely used for traction motor control in electric automobiles, trolley cars, marine hoists, forklifts trucks, and mine haulers. They provide high efficiency, good acceleration control and fast dynamic response. They can be used in regenerative braking of DC motors to return energy back into the supply. This attribute results in energy savings for transportation systems with frequent steps. DC converters are used in DC voltage regulators; and also are used, with an inductor in conjunction, to generate a DC current source, specifically for the current source inverter. [1] 1.2 PURPOSE OF THE PROJECT Efficiency, size, and cost are the primary advantages of switching power converters when compared to linear converters. The switching power converter efficiencies can run between 70- 80%, whereas linear converters are usually 30% efficient. The DC-DC Switching Boost Converter is designed to provide an efficient method of taking a given DC voltage supply and boosting it to a desired value. 1 Chapter 2 BACKGROUND AND LITERATURE OVERVIEW 2.1 OVERVIEW Power for the boost converter can come from any suitable DC sources, such as DC generators, batteries, solar panels and rectifiers. The method that changes one DC voltage to a different DC voltage is called DC to DC conversion. Generally, a boost converter is a DC to DC converter with an output voltage greater than the source voltage. It is sometimes called a step-up converter since it “steps up” the source voltage. [2] 2.2 HISTORY For high efficiency, the SMPS switch must turn on and off quickly and have very less losses. The coming of a commercial semiconductor switch such as the boost converter in the 1950s represented a major milestone that made SMPSs possible. The main DC to DC converters were developed in the early 1960s when semiconductor switches were available. Switched systems such as SMPS are a challenge to design since its model depends on whether a switch is opened or closed. R. D. Middlebrook from Caltech in 1977 published the models for DC to DC converters in market today. He averaged the circuit configurations for each switch state in a technique called state-space average modelling. This simplification resulted in reduction of two systems into one. This model led to insightful design equations which helped SMPS growth. [2] 2.3 APPLICATIONS Battery powered systems often stack cells in series to obtain higher voltage. However, sufficient heaping of cells is not possible in many high voltage applications due to insufficient space. Boost converters can increase the voltage and reduce the cell numbers. Two battery-powered applications that use boost converters are hybrid electric vehicles (HEV) and lighting systems. The NHW20 model Toyota Prius HEV utilizes 500 V. If there is no boost converter, the HEV would need nearly 417 cells to power its motor. In reality, a Prius actually uses only 168 cells and boosts the battery voltage from 202 V to 500 V. On a smaller scale application, boost converters also power devices such as portable lighting systems and emergency lights. A white LED typically 2 requires 3.3 V to function, and a boost converter can step up the voltage from a single 1.5 V alkaline cell to power the light. It can also produce higher voltages to operate cold cathode fluorescent tubes (CCFL) in devices such as LCD backlights and some flashlights. A boost converter is used as the voltage increase mechanism in the circuit known as the 'Joule thief', which is a circuit topology used with low power battery applications, and is purposed at the ability of a boost converter to 'steal' the remaining energy in a battery. The energy remaining would otherwise be wasted since the low voltage of a nearly depleted battery makes it unusable for a load. The remaining energy would otherwise remain untapped because many applications do not allow enough current to flow through a load when voltage degrades. This occurs as batteries are degraded, and is a characteristic of a normal battery. [2][3] There are a range of uses for a DC-DC boost converter. Travelers need to carry such devices when they want to bring electronics from home and the supply of current in a foreign country differs from that which is present at their home. Sometimes only a plug converter is required, but in other cases, plugging electronics directly into the power supply could damage the devices.